Some atmospheric issues have been solved effectively as a result of a variety of mechanisms and where successful action has been taken, the benefits far exceed the costs. Significant progress has, for example, been made in reaching the internationally agreed goal of the Montreal Protocol to protect the stratospheric ozone (ozone in the upper atmosphere) layer. A drastic reduction in both the production and use of ozone- depleting substances&nbsp;(ODS)&nbsp;has been achieved, resulting in a 31 per cent improvement in ODS indicators at mid latitudes since 1994, and the predicted avoidance of 22 million cases of cataract for people born between 1985 and 2100 in the United States of America alone.

For other issues, such as the reduction of indoor and outdoor PM and emissions of sulphur and nitrogen compounds, progress&nbsp;has been mixed. Tropospheric ozone (ozone in the lower atmosphere) remains a significant problem and is proving difficult to address.

In parts of Africa, Asia and Latin America, where urban PM levels remain far in excess of international guidelines, the concern is high. Similarly, the dust-haze phenomenon in the Middle East is of concern. Improved public information on local air quality could contribute to raising awareness of this issue.